荒漠灌丛微生境土壤温度的时空变异特征——灌丛与降水的影响

Effects of Shrubs and Precipitation on Spatial-temporal Variation of Soil Temperature at the Microhabitats Induced by Desert Shrubs

对干旱区优势固沙灌木柠条群落不同微生境(灌丛外和灌丛下)的土壤温度(0cm、5cm、10cm和20cm剖面深度)进行了连续测定,对比分析了晴天、降水日与灌丛对其微生境土壤温度时空变异的影响。结果表明:降水和植被灌丛对土壤温度均具有显著影响。在无雨日,受灌丛遮阴影响,灌丛外土壤温度明显高于灌丛下相同深度的土壤温度;在降水日,土壤温度主要受降水影响,降水使土壤温度明显降低,灌丛的影响作用减弱,灌丛下和灌丛外同一剖面深度的土壤温度差异较小。无雨日土壤温度日变化呈单峰型正弦曲线,随剖面深度增加,土壤温度振幅逐渐减小,峰值出现时间滞后,土壤温度垂直分布变化呈现4种典型变化曲线。夜间(日落至日出)柠条灌丛下地表温度(0cm土壤温度)比灌丛外地表温度略高。降水日土壤温度日变化随降水过程的持续呈逐渐递减趋势,土壤温度垂直分布变化表现为随深度增加而递增的趋势。

Soil temperatures at the 0, 5, 10, 20 cm depths were monitored continuously at different micro- habitats （beneath shrub canopy, BSC; bare intershrub spaces, BIS） induced by Caragana korshinskii, one of the dominant sand fixing shrubs in arid regions, respectively. The purpose of this study was to assess the effects of shrub on the spatial-temporal variability of soil temperature in rainy days and cloudless days. Re- sults indicated that both precipitation and vegetation significantly affected soil temperature. In days with no precipitation, soil temperatures at the area BSC were significantly lower than in the BIS at the same soil depth due to the shading effects of shrub canopy. In rainy days, soil temperatures were affected mainly by precipitation and the shrub canopy had a negligible effect on soil temperature. Little difference in soil tem- perature at the same soil depth was found between the area BSC and in the BIS. Diurnal variations of soil temperature showed a unimodal sinusoidal curve in cloudless days. The amplitude of soil temperature tended to decrease and a hysteresis of the diurnal maximum soil temperature existed at deeper soil depths. Vertical fluctuations of soil temperature displayed four typical curves. In the nighttime （approximately from sunset to sunrise）, surface temperature at the area BSC was higher than in the BIS. In rainy days, diurnal variations in soil temperature decreased exclusively as rainfall continued and the vertical fluctuations of soil temperature showed an increased tendency with increasing soil depth.